Analysis of Soil Nitrate Ion Selective Electrode (ISE) Sensor using Arduino UNO

The ecological concern over soil and groundwater pollution caused by agricultural activities has led to the growing interest in precision agriculture. One of the most common types of fertilizer is the nitrogen fertilizer which needed in major amount for plant growth. Over fertilization will contaminate soil and groundwater which can have adverse effect on environment and human health. The main purpose of this research is to measure soil nitrate concentration using nitrate ion-selective electrode (ISE) sensor and Arduino programmable microcontroller. The optimum soil-to-water ratio and the effect of soil solution clarity will be investigated. Standard sampling procedures was conducted at oil palm plantation area, Felda Bukit Goh, Pahang, Malaysia. Validation of the results were carried out in the laboratory. The recorded data indicated accurate readings for Nitrate ISE Arduino was R² = 0.84. The soil-to-water ratio of 1:2.5 was observed as an optimal proportion ISE analysis. A clear soil solution was crucial for maintaining the accuracy of ISE sensor, to avoid declining of 46.2% accuracy. These results could assist researchers and farmers to accurately monitor the concentrations of soil nitrate on the field effectively as well as an insight to ISE sensor with Arduino technologies

The fabrication of potentiometric membrane sensors and their applications

Ionophore-incorporated PVC-membrane sensors are well-established analytical tools routinely used for the selective and direct measurement of a wide variety of different ions in complex biological and environmental samples. The key ingredient of such plasticized PVC-members is the involved ionophore, defining the selectivity of the electrodes complex formation with the cation of interest. In the past few years, the development of new ion-selective electrodes for various ions has been reported inthe literature

Simple and robust ion-selective electrodes for bio/environmental analysis

Chemical sensors have gone through a lot of optimisation renaissance over the years to have come from a typical bench-top tool for measurements of ions in standard solutions, to a more promising analytical technique capable of measuring the activities of free un-complexed nutrients in environmentally and biologically important samples. With various health issues arising due to the increasing anthropogenic contributions of man to the environment amongst other factors, and due to the need for more routine analysis especially do-it-yourself (DIY) of several analytes in physiological samples for clinical purposes, it is therefore imperative that simple, cheap, but robust sensors are developed, and optimised to meet these emerging needs. First part of this work involved fabricating solid-contact ion selective electrodes (SC-ISEs) based on the mechanical abrasion of graphite on easily modified acetate paper. Similarly results from the impedance spectra and the water layer test for electrodes with or without a conducting polymer (CP) layer indicated the suitability of the procedure. The fabricated paper electrodes importantly showed fast response time and great potential stability over the course of fourteen days. The same fabrication methodology was used to produce stable and functional solid-state paper reference electrode, and then, combined with other graphite-based paper ISEs to yield a single-strip solid contact electrode for simultaneous measurements of nitrate and ammonium in environmental samples. Satisfactory results from the comparison of measured concentrations by potentiometry and standard reference methods indicated this simplified electrode platform, designed from household materials can be used as a cheaper alternative to other solid contact electrodes. Subsequent works in this thesis involved the application of the fabricated SC-ISEs in optimization of measurement procedures of environmentally important nutrients and biologically important analytes. Routine monitoring of reactive nitrogen Nr (majorly NH4+ and NO3-) in environmental samples including soils from major land types is important to soil management system. In achieving a relatively rapid turn-around time of analysis, inorganic N species were extracted from various soil types using a single extracting solution (0.1 M MgSO4). Extractable-NH4+ and -NO3- in soils, and bioavailable NH4+ and NO3- in water samples measured concurrently using paper ISEs showed similar results to standard analytical methods. The analysis of urinary iodine (UI) is important to the public health due to serious health issues attached to its deficiency. As a result, iodide-selective electrodes based on [9] Mercuracarborand-3 (MC3) and [12] Mercuracarborand-4 (MC4) as ionophores, and NPOE and DOS as plasticizers were developed with a view to evaluate the concentration of iodide in urine. However, ion-selective electrodes (ISEs) are one of the very few experimental techniques whose limit of detection (LOD) is not defined as signal-to-noise ratio. As a result, the Bayesian model was applied to estimate the activities of nitrate and ammonium in soil and water samples, and iodide in urine samples. While the Bayesian estimates for nitrate and ammonium ions were satisfactory, significant discrepancy of estimated results for iodide in urine shows more work needs to be done in relation to designing more selective ionophores to complement non-linear approaches

Simple and robust ion-selective electrodes for bio/environmental analysis

Chemical sensors have gone through a lot of optimisation renaissance over the years to have come from a typical bench-top tool for measurements of ions in standard solutions, to a more promising analytical technique capable of measuring the activities of free un-complexed nutrients in environmentally and biologically important samples. With various health issues arising due to the increasing anthropogenic contributions of man to the environment amongst other factors, and due to the need for more routine analysis especially do-it-yourself (DIY) of several analytes in physiological samples for clinical purposes, it is therefore imperative that simple, cheap, but robust sensors are developed, and optimised to meet these emerging needs.First part of this work involved fabricating solid-contact ion selective electrodes (SC-ISEs) based on the mechanical abrasion of graphite on easily modified acetate paper. Similarly results from the impedance spectra and the water layer test for electrodes with or without a conducting polymer (CP) layer indicated the suitability of the procedure. The fabricated paper electrodes importantly showed fast response time and great potential stability over the course of fourteen days. The same fabrication methodology was used to produce stable and functional solid-state paper reference electrode, and then, combined with other graphite-based paper ISEs to yield a single-strip solid contact electrode for simultaneous measurements of nitrate and ammonium in environmental samples. Satisfactory results from the comparison of measured concentrations by potentiometry and standard reference methods indicated this simplified electrode platform, designed from household materials can be used as a cheaper alternative to other solid contact electrodes.Subsequent works in this thesis involved the application of the fabricated SC-ISEs in optimization of measurement procedures of environmentally important nutrients and biologically important analytes.Routine monitoring of reactive nitrogen Nr (majorly NH4+ and NO3-) in environmental samples including soils from major land types is important to soil management system. In achieving a relatively rapid turn-around time of analysis, inorganic N species were extracted from various soil types using a single extracting solution (0.1 M MgSO4). Extractable-NH4+ and -NO3- in soils, and bioavailable NH4+ and NO3- in water samples measured concurrently using paper ISEs showed similar results to standard analytical methods.The analysis of urinary iodine (UI) is important to the public health due to serious health issues attached to its deficiency. As a result, iodide-selective electrodes based on [9] Mercuracarborand-3 (MC3) and [12] Mercuracarborand-4 (MC4) as ionophores, and NPOE and DOS as plasticizers were developed with a view to evaluate the concentration of iodide in urine.However, ion-selective electrodes (ISEs) are one of the very few experimental techniques whose limit of detection (LOD) is not defined as signal-to-noise ratio. As a result, the Bayesian model was applied to estimate the activities of nitrate and ammonium in soil and water samples, and iodide in urine samples. While the Bayesian estimates for nitrate and ammonium ions were satisfactory, significant discrepancy of estimated results for iodide in urine shows more work needs to be done in relation to designing more selective ionophores to complement non-linear approaches

Analysis of relevant technical issues and deficiencies of the existing sensors and related initiatives currently set and working in marine environment. New generation technologies for cost-effective sensors

The last decade has seen significant growth in the field of sensor networks, which are currently collecting large amounts of environmental data. This data needs to be collected, processed, stored and made available for analysis and interpretation in a manner which is meaningful and accessible to end users and stakeholders with a range of requirements, including government agencies, environmental agencies, the research community, industry users and the public. The COMMONSENSE project aims to develop and provide cost-effective, multi-functional innovative sensors to perform reliable in-situ measurements in the marine environment. The sensors will be easily usable across several platforms, and will focus on key parameters including eutrophication, heavy metal contaminants, marine litter (microplastics) and underwater noise descriptors of the MSFD. The aims of Tasks 2.1 and 2.2 which comprise the work of this deliverable are: • To obtain a comprehensive understanding and an up-to-date state of the art of existing sensors. • To provide a working basis on “new generation” technologies in order to develop cost-effective sensors suitable for large-scale production. This deliverable will consist of an analysis of state-of-the-art solutions for the different sensors and data platforms related with COMMONSENSE project. An analysis of relevant technical issues and deficiencies of existing sensors and related initiatives currently set and working in marine environment will be performed. Existing solutions will be studied to determine the main limitations to be considered during novel sensor developments in further WP’s. Objectives & Rationale The objectives of deliverable 2.1 are: • To create a solid and robust basis for finding cheaper and innovative ways of gathering data. This is preparatory for the activities in other WPs: for WP4 (Transversal Sensor development and Sensor Integration), for WP(5-8) (Novel Sensors) to develop cost-effective sensors suitable for large-scale production, reducing costs of data collection (compared to commercially available sensors), increasing data access availability for WP9 (Field testing) when the deployment of new sensors will be drawn and then realized

개별 이온 및 작물 생육 센싱 기반의 정밀 수경재배 양액 관리 시스템

학위논문 (박사) -- 서울대학교 대학원 : 농업생명과학대학 바이오시스템·소재학부(바이오시스템공학), 2020. 8. 김학진.In current closed hydroponics, the nutrient solution monitoring and replenishment are conducted based on the electrical conductivity (EC) and pH, and the fertigation is carried out with the constant time without considering the plant status. However, the EC-based management is unable to detect the dynamic changes in the individual nutrient ion concentrations so the ion imbalance occurs during the iterative replenishment, thereby leading to the frequent discard of the nutrient solution. The constant time-based fertigation inevitably induces over- or under-supply of the nutrient solution for the growing plants. The approaches are two of the main causes of decreasing water and nutrient use efficiencies in closed hydroponics. Regarding the issues, the precision nutrient solution management that variably controls the fertigation volume and corrects the deficient nutrient ions individually would allow both improved efficiencies of fertilizer and water use and increased lifespan of the nutrient solution. The objectives of this study were to establish the precision nutrient solution management system that can automatically and variably control the fertigation volume based on the plant-growth information and supply the individual nutrient fertilizers in appropriate amounts to reach the optimal compositions as nutrient solutions for growing plants. To achieve the goal, the sensing technologies for the varying requirements of water and nutrients were investigated and validated. Firstly, an on-the-go monitoring system was constructed to monitor the lettuces grown under the closed hydroponics based on the nutrient film technique for the entire bed. The region of the lettuces was segmented by the excess green (ExG) and Otsu method to obtain the canopy cover (CC). The feasibility of the image processing for assessing the canopy (CC) was validated by comparing the computed CC values with the manually analyzed CC values. From the validation, it was confirmed the image monitoring and processing for the CC measurements were feasible for the lettuces before harvest. Then, a transpiration rate model using the modified Penman-Monteith equation was fitted based on the obtained CC, radiation, air temperature, and relative humidity to estimate the water need of the growing lettuces. Regarding the individual ion concentration measurements, two-point normalization, artificial neural network, and a hybrid signal processing consisting of the two-point normalization and artificial neural network were compared to select an effective method for the ion-selective electrodes (ISEs) application in continuous and autonomous monitoring of ions in hydroponic solutions. The hybrid signal processing showed the most accuracy in sample measurements, but the vulnerability to the sensor malfunction made the two-point normalization method with the most precision would be appropriate for the long-term monitoring of the nutrient solution. In order to determine the optimal injection amounts of the fertilizer salts and water for the given target individual ion concentrations, a decision tree-based dosing algorithm was designed. The feasibility of the dosing algorithm was validated with the stepwise and varying target focusing replenishments. From the results, the ion-specific replenishments formulated the compositions of the nutrient solution successfully according to the given target values. Finally, the proposed sensing and control techniques were integrated to implement the precision nutrient solution management, and the performance was verified by a closed lettuce cultivation test. From the application test, the fertigation volume was reduced by 57.4% and the growth of the lettuces was promoted in comparison with the constant timer-based fertigation strategy. Furthermore, the system successfully maintained the nutrient balance in the recycled solution during the cultivation with the coefficients of variance of 4.9%, 1.4%, 3.2%, 5.2%, and 14.9%, which were generally less than the EC-based replenishment with the CVs of 6.9%, 4.9%, 23.7%, 8.6%, and 8.3% for the NO3, K, Ca, Mg, and P concentrations, respectively. These results implied the developed precision nutrient solution management system could provide more efficient supply and management of water and nutrients than the conventional methods, thereby allowing more improved water and nutrient use efficiencies and crop productivity.현재의 순환식 수경재배 시스템에서 양액의 분석과 보충은 전기전도도 (EC, electrical conductivity) 및 pH를 기반으로 수행되고 있으며, 양액의 공급은 작물의 생육 상태에 대한 고려 없이 항상 일정한 시간 동안 펌프가 동작하여 공급되는 형태이다. 그러나 EC 기반의 양액 관리는 개별 이온 농도의 동적인 변화를 감지할 수 없어 반복되는 보충 중 불균형이 발생하게 되어 양액의 폐기를 야기하며, 고정된 시간 동안의 양액 공급은 작물에 대해 과잉 또는 불충분한 물 공급으로 이어져 물 사용 효율의 저하를 일으킨다. 이러한 문제들에 대해, 개별 이온 농도에 대해 부족한 성분만을 선택적으로 보충하고, 작물의 생육 정도에 기반하여 필요한 수준에 맞게 양액을 공급하는 정밀 농업에 기반한 양액 관리를 수행하면 물과 비료 사용 효율의 향상과 양액의 재사용 기간 증진을 기대할 수 있다. 본 연구의 목적은 자동으로, 그리고 가변적으로 작물 생육 정보에 기반하여 양액 공급량을 제어하고, 작물 생장에 적합한 조성에 맞게 현재 양액의 이온 농도 센싱에 기반하여 적절한 수준만큼의 물과 개별 양분 비료를 보충할 수 있는 정밀 수경재배 양액 관리 시스템을 개발하는 것이다. 해당 목표를 달성하기 위해, 변이하는 물과 양분 요구량을 측정할 수 있는 모니터링 기술들을 분석하고 각 모니터링 기술들에 대한 검증을 수행하였다. 먼저, 작물의 물 요구량을 실시간으로 관측할 수 있는 영상 기반 측정 기술을 조사하였다. 영상 기반 분석 활용을 위해 박막경 기반의 순환식 수경재배 환경에서 자라는 상추의 이미지들을 전체 베드에 대해 수집할 수 있는 영상 모니터링 시스템을 구성하였고, 수집한 영상 중 상추 부분만을 excess green (ExG)과 Otsu 방법을 통해 분리하여 투영작물면적 (CC, canopy cover)을 획득하였다. 영상 처리 기술의 적용성 평가를 위해 직접 분석한 투영작물면적 값과 이를 비교하였다. 비교 검증 결과에서 투영작물면적 측정을 위한 영상 수집 및 분석이 수확 전까지의 상추에 대해 적용 가능함을 확인하였다. 이후 수집한 투영작물면적과 기온, 상대습도, 일사량을 기반으로 생육 중인 상추들이 요구하는 물의 양을 예측하기 위해 Penman-Monteith 방정식 기반의 증산량 예측 모델을 구성하였으며 실제 증산량과 비교하였을 때 높은 일치도를 확인하였다. 개별 이온 농도 측정과 관련하여서는, 이온선택성전극 (ISE, ion-selective electrode)를 이용한 수경재배 양액 내 이온의 연속적이고 자율적인 모니터링 수행을 위해 2점 정규화, 인공신경망, 그리고 이 둘을 복합적으로 구성한 하이브리드 신호 처리 기법의 성능을 비교하여 분석하였다. 분석 결과, 하이브리드 신호 처리 방식이 가장 높은 정확성을 보였으나, 센서 고장에 취약한 신경망 구조로 인해 장기간 모니터링 안정성에 있어서는 가장 높은 정밀도를 가진 2점 정규화 방식을 센서 어레이에 적용하는 것이 적합할 것으로 판단하였다. 또한, 주어진 개별 이온 농도 목표값에 맞는 비료 염 및 물의 최적 주입량을 결정하기 위해 의사결정트리 구조의 비료 투입 알고리즘을 제시하였다. 제시한 비료 투입 알고리즘의 효과에 대해서는 순차적인 목표에 대한 보충 및 특정 성분에 대해 집중적인 변화를 부여한 보충 수행 실험을 통해 검증하였으며, 그 결과 제시한 알고리즘은 주어진 목표값들에 따라 성공적으로 양액을 조성하였음을 확인하였다. 마지막으로, 제시되었던 센싱 및 제어 기술들을 통합하여 NFT 기반의 순환식 수경재배 배드에 상추 재배를 수행하여 실증하였다. 실증 실험에서, 종래의 고정 시간 양액 공급 대비 57.4%의 양액 공급량 감소와 상추 생육의 촉진을 확인하였다. 동시에, 개발 시스템은 NO3, K, Ca, Mg, 그리고 P에 대해 각각 4.9%, 1.4%, 3.2%, 5.2%, 그리고 14.9% 수준의 변동계수 수준을 보여 EC기반 보충 방식에서 나타난 변동계수 6.9%, 4.9%, 23.7%, 8.6%, 그리고 8.3%보다 대체적으로 우수한 이온 균형 유지 성능을 보였다. 이러한 결과들을 통해 개발 정밀 관비 시스템이 기존보다 효율적인 양액의 공급과 관리를 통해 양액 이용 효율성과 생산성의 증진에 기여할 수 있을 것으로 판단되었다.CHAPTER 1. INTRODUCTION 1 BACKGROUND 1 Nutrient Imbalance 2 Fertigation Scheduling 3 OBJECTIVES 7 ORGANIZATION OF THE DISSERTATION 8 CHAPTER 2. LITERATURE REVIEW 10 VARIABILITY OF NUTRIENT SOLUTIONS IN HYDROPONICS 10 LIMITATIONS OF CURRENT NUTRIENT SOLUTION MANAGEMENT IN CLOSED HYDROPONIC SYSTEM 11 ION-SPECIFIC NUTRIENT MONITORING AND MANAGEMENT IN CLOSED HYDROPONICS 13 REMOTE SENSING TECHNIQUES FOR PLANT MONITORING 17 FERTIGATION CONTROL METHODS BASED ON REMOTE SENSING 19 CHAPTER 3. ON-THE-GO CROP MONITORING SYSTEM FOR ESTIMATION OF THE CROP WATER NEED 21 ABSTRACT 21 INTRODUCTION 21 MATERIALS AND METHODS 23 Hydroponic Growth Chamber 23 Construction of an On-the-go Crop Monitoring System 25 Image Processing for Canopy Cover Estimation 29 Evaluation of the CC Calculation Performance 32 Estimation Model for Transpiration Rate 32 Determination of the Parameters of the Transpiration Rate Model 33 RESULTS AND DISCUSSION 35 Performance of the CC Measurement by the Image Monitoring System 35 Plant Growth Monitoring in Closed Hydroponics 39 Evaluation of the Crop Water Need Estimation 42 CONCLUSIONS 46 CHAPTER 4. HYBRID SIGNAL-PROCESSING METHOD BASED ON NEURAL NETWORK FOR PREDICTION OF NO3, K, CA, AND MG IONS IN HYDROPONIC SOLUTIONS USING AN ARRAY OF ION-SELECTIVE ELECTRODES 48 ABSTRACT 48 INTRODUCTION 49 MATERIALS AND METHODS 52 Preparation of the Sensor Array 52 Construction and Evaluation of Data-Processing Methods 53 Preparation of Samples 57 Procedure of Sample Measurements 59 RESULTS AND DISCUSSION 63 Determination of the Artificial Neural Network (ANN) Structure 63 Evaluation of the Processing Methods in Training Samples 64 Application of the Processing Methods in Real Hydroponic Samples 67 CONCLUSIONS 72 CHAPTER 5. DECISION TREE-BASED ION-SPECIFIC NUTRIENT MANAGEMENT ALGORITHM FOR CLOSED HYDROPONICS 74 ABSTRACT 74 INTRODUCTION 75 MATERIALS AND METHODS 77 Decision Tree-based Dosing Algorithm 77 Development of an Ion-Specific Nutrient Management System 82 Implementation of Ion-Specific Nutrient Management with Closed-Loop Control 87 System Validation Tests 89 RESULTS AND DISCUSSION 91 Five-stepwise Replenishment Test 91 Replenishment Test Focused on The Ca 97 CONCLUSIONS 99 CHAPTER 6. ION-SPECIFIC AND CROP GROWTH SENSING BASED NUTRIENT SOLUTION MANAGEMENT SYSTEM FOR CLOSED HYDROPONICS 101 ABSTRACT 101 INTRODUCTION 102 MATERIALS AND METHODS 103 System Integration 103 Implementation of the Precision Nutrient Solution Management System 106 Application of the Precision Nutrient Solution Management System to Closed Lettuce Soilless Cultivation 112 RESULTS AND DISCUSSION 113 Evaluation of the Plant Growth-based Fertigation in the Closed Lettuce Cultivation 113 Evaluation of the Ion-Specific Management in the Closed Lettuce Cultivation 118 CONCLUSIONS 128 CHAPTER 7. CONCLUSIONS 130 CONCLUSIONS OF THE STUDY 130 SUGGESTIONS FOR FUTURE STUDY 134 LIST OF REFERENCES 136 APPENDIX 146 A1. Python Code for Controlling the Image Monitoring and CC Calculation 146 A2. Ion Concentrations of the Solutions used in Chapter 4 (Unit: mg∙L−1) 149 A3. Block Diagrams of the LabVIEW Program used in Chapter 4 150 A4. Ion Concentrations of the Solutions used in Chapters 5 and 6 (Unit: mg∙L−1) 154 A5. Block Diagrams of the LabVIEW Program used in the Chapters 5 and 6 155 ABSTRACT IN KOREAN 160Docto

TECHNIQUES FOR STUDYING THE BIOGEOCHEMISTRY OF NUTRIENTS IN THE TAMAR CATCHMENT

Chapter One describes nitrogen and phosphorus species in the aquatic environment, their role in eutrophication, current legislation relevant to nutrient water quality and catchment management and the role of predictive modelling of nutrient export with respect to the management of river catchments. It also summarises analytical techniques for the determination of nitrogen and phosphorus species in natural waters and the use of generic ecotoxicological assays to link nutrient water quality and organism health. Data integrity is essential to biogeochemical studies that inform scientific research and environmental management. Reliable, accurate data permit valid conclusions to be drawn. The quality assurance and quality control measures undertaken to ensure good analytical data in this study, including participation in the certification of a seawater certified reference material for nutrients (MOOS-1), are discussed in Chapter Two. In Chapter Three, the nutrient biogeochemistry of the waters leaving the Tamar catchment and entering the Tamar estuary is discussed. Historical nutrient and physico-chemical data for the Tamar River at Gunnislake were used to identify long-term environmental trends (1974 to 2004) and nutrient and physico-chemical data collected in this study between May 2003 and May 2004 was used to identify short-term trends over the study period. The nutrient export coefficient modelling approach was used to model phosphorus and nitrogen export from the Tamar catchment (Chapter Four). A TP export model from the Tamar catchment was successfully constructed using historical land use data and catchment demographics, calibrated with hindcasted water quality data, and validated with TP field data (May 2003 and May 2004) collected in this study. Modelled P (43. 5 tonnes P yˉ¹) export agreed within 8 % with the measured P load (40.1 tonnes P yˉ¹). An annual TN model was also constructed and calibrated for the Tamar catchment using the May 2003 to May 2004 field data. The calibrated model agreed within I % of the measured TN export (2053 tonnes N yˉ¹). The development and deployment of a portable Fl analyser for continuous, real-time monitoring of FRP in the Tamar catchment is discussed in Chapter Five. The optimised method can be used for the determination of FRP in freshwater systems (4-150 µg Lˉ¹ P) and in coastal waters (10-150 µg Lˉ¹ P) and is capable of sampling with high temporal resolution (up to 15 samples hˉ¹) . The analyser was used in situ (bank-side and shipboard deployment) to provide real-time FRP data and in the laboratory to determine FRP in freshwater samples. All data were in good agreement with values obtained using a validated air-segmented, continuous flow laboratory reference method The acute toxicity of nitrate and nitrite on the freshwater swan mussel, Anodonta cygnea, was investigated (Chapter Six). A 96 h LC50 value of 222 mg Lˉ¹ N for the exposure of A. cygnea to nitrite was established in this study. Toxicity studies indicated that nitrate was not toxic to A. cygnea. Established indicators of physiological stress were used to determine the effect of environmentally high and extreme levels of nitrite on A. cygnea. There was no significant difference in cardiac activity, condition index or lysosomal stability between control organisms (0 mg Lˉ¹ N) and organisms exposed to sub-lethal nitrite concentrations (0.1, 1.0, 22.2 mg Lˉ¹ N). Therefore, nitrite concentrations encountered in typical freshwater catchments such as the Tamar catchment are unlikely to induce physiological stress in A.cygnea

A review of the state-of-the-art wastewater quality characterization and measurement technologies. Is the shift to real-time monitoring nowadays feasible?

Efficient characterization of wastewater stream quality is vital to ensure the safe discharge or reuse of treated wastewater (WW). There are numerous parameters employed to characterize water quality, some required by directives (e.g. biological oxygen demand (BOD), total nitrogen (TN), total phosphates (TP)), while others used for process controls (e.g. flow, temperature, pH). Well-accepted methods to assess these parameters have traditionally been laboratory-based, taking place either off-line or at-line, and presenting a significant delay between sampling and result. Alternative characterization methods can run in-line or on-line, generally being more cost-effective. Unfortunately, these methods are often not accepted when providing information to regulatory bodies. The current review aims to describe available laboratory-based approaches and compare them with innovative real-time (RT) solutions. Transitioning from laboratory-based to RT measurements means obtaining valuable process data, avoiding time delays, and the possibility to optimize the (WW) treatment management. A variety of sensor categories are examined to illustrate a general framework in which RT applications can replace longer conventional processes, with an eye toward potential drawbacks. A significant enhancement in the RT measurements can be achieved through the employment of advanced soft-sensing techniques and the Internet of Things (IoT), coupled with machine learning (ML) and artificial intelligence (AI)

Membrane Based intensification of ammonia removal from wastewater

The aim of this research was to study a novel membrane based oxygen intensification system to enhance a biological wastewater treatment process for ammonia removal. Specifically, this work is concerned with the biological nitrification process which occurs in ion exchange packed columns during ammonia removal from wastewater. Two types of commercial clinoptilolite were used, namely KMI and BIT, as ion exchangers. Removal of ammonium ion by ion exchange offers a number of advantages such as the capability to handle shock loadings and to purify wastewater to a very high specification. Also, ion exchangers can be used to provide a solid surface for bacterial growth which enhances performance. The uptake removal rates of ammonium ions onto KMI and BIT clinoptilolite using DI water, RO water, and filtered tap water were examined. The presence of major metal ions that normally exist in wastewater such as K+, Ca++, and Mg++ and their impact on ammonia adsorption was tested. The experimental data were fitted using Langmuir and Freundlich isotherms and compared to related works done previously. KMI clinoptilolite exhibited the highest uptake capacity, and KMI clinoptilolite preference for the metal ions was found to be in the order Mg++¡ÖK+Ca++. The kinetics of the ammonium ion removal were studied at bench scale using KMI and BIT clinoptilolite. The process variables include: initial ammonia concentration, amount of clinoptilolite in contact with the solution, clinoptilolite particle size, and mixing speed. To model the kinetics removal rates two types of diffusion was assumed to be possible rate limiting steps, namely the external film diffusion and the intraparticle diffusion. Two models were selected to fit the controlled diffusion resistances, Furusawa-Smith to model the external film resistance and McKay model to model the intraparticle film resistance. The values of the external and internal mass transfer coefficients were calculated and tabulated. Five air permeable membranes were used, four porous membranes and a dense membrane. The porous membranes were Polyethersulfone (PES), Polytetrafluoroethylene (PTFE), Polypropylene (PP), and Nylon. The dense membrane was a silicon tube membrane. All membranes were assessed for aeration. The overall mass transfer coefficients were calculated using the two-film theory model. The highest oxygen transfer rate was observed in PTFE membrane, and in the following order of lower performance PP PES Nylon silicon tube. For the column studies, different loading rates were used, 0.96, 0.25, and 0.03 Kg N/(m3day) depending on the type of the experiment. For the bacteria-free silicon membrane column, the inlet ammonia concentration, bed height, and inlet flowrate were examined. Biologically activated silicon membrane column exhibited no difference in the ammonia removal comparing to bacteria-free column under the same operating conditions. The porous membrane columns were designed to enhance the aeration for the combined biologically active ion exchanger packed bed column. It was found that the porous membrane columns were significantly enhanced by introducing the nitrifying bacteria into the columns. For example, the uptake capacity of PP membrane column was increased from 0.43 to 0.67 meq/g by introducing the biological material into the PP column. The breakthrough bed volumes (BVs) were estimated and the uptake column capacities were calculated for all the used columns. The breakthrough curves were modeled using the Bohart-Adams and Thomas models. To assess the bio-regeneration as an alternative to the chemical regeneration, nitrifying bacteria circulated in PP and PES columns to treat exhausted KMI clinoptilolite. The results showed that some regeneration may be achieved, but complete regeneration would require higher concentrations of biomass which is recommended for future study